Tarbosaurus
Tarbosaurus | |
---|---|
Skeleton on exhibit in Maryland Science Center | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | †Tyrannosauridae |
Subfamily: | †Tyrannosaurinae |
Clade: | † Tyrannosaurini
|
Genus: | †Tarbosaurus Maleev, 1955b |
Type species | |
†Tarbosaurus bataar Maleev, 1955a
| |
Synonyms | |
Species synonymy
|
Tarbosaurus (
Although many species have been named, modern paleontologists recognize only one species, T. bataar. Some experts see this species as an Asian representative of the North American genus Tyrannosaurus, which would make the genus Tarbosaurus redundant. Tarbosaurus and Tyrannosaurus, if not synonymous, are considered to be very closely related genera. Alioramus, also from Mongolia, has previously been thought by some authorities to be the closest relative of Tarbosaurus, though this has since been disproven with the discovery of Qianzhousaurus and the description of the tyrannosaurine tribe Alioramini.
Like most known tyrannosaurids, Tarbosaurus was a large
Tarbosaurus lived in a humid
Discovery and naming
In 1946, a joint
A 1965 paper by A. K. Rozhdestvensky recognized all of Maleev's specimens as different growth stages of the same species, which he believed to be distinct from the North American Tyrannosaurus. He created a new combination, Tarbosaurus bataar, to include all the specimens described in 1955 and newer material.[7] Later authors, including Maleev himself,[8] agreed with Rozhdestvensky's analysis, although some used the name Tarbosaurus efremovi instead of T. bataar.[9] American paleontologist Ken Carpenter re-examined the material in 1992. He concluded that it belonged to the genus Tyrannosaurus, as originally published by Maleev, and lumped all the specimens into the species Tyrannosaurus bataar (except the remains that Maleev had named Gorgosaurus novojilovi). Carpenter thought this specimen represented a separate, smaller genus of tyrannosaurid, which he called Maleevosaurus novojilovi.[10] George Olshevsky created the new generic name Jenghizkhan (after Genghis Khan) for Tyrannosaurus bataar in 1995, while also recognizing Tarbosaurus efremovi and Maleevosaurus novojilovi, for a total of three distinct, contemporaneous genera from the Nemegt Formation.[11] A 1999 study subsequently reclassified Maleevosaurus as a juvenile Tarbosaurus.[12] All research published since 1999 recognizes only a single species, which is either called Tarbosaurus bataar[13][14][15] or Tyrannosaurus bataar.[16]
After the original Soviet-Mongolian expeditions in the 1940s,
Poached specimens
Tarbosaurus fossils are only found around the Gobi Desert of Mongolia and China, both of which ban their export, though some specimens have been looted by private collectors.
Synonyms
Albertosaurus periculosus, Tyrannosaurus luanchuanensis, Tyrannosaurus turpanensis, and Chingkankousaurus fragilis were all considered synonyms of Tarbosaurus in the second edition of the Dinosauria, but Chingkankousaurus has been assessed as dubious by Brusatte et al. (2013).[13][28]
Named in 1976 by Sergei Kurzanov, Alioramus is another genus of tyrannosaurid from slightly older sediments in Mongolia.[29] Several analyses have concluded Alioramus was quite closely related to Tarbosaurus.[4][14] It was described as an adult, but its long, low skull is characteristic of a juvenile tyrannosaurid. This led Currie to speculate that Alioramus might represent a juvenile Tarbosaurus, but he noted that the much higher tooth count and row of crests on top of the snout suggested otherwise.[30]
Skin impressions and footprints
Skin impressions were recovered from a large skeleton at the Bugiin Tsav locality that was subsequently destroyed by poachers. These impressions show non-overlapping scales with an average diameter of 2.4 millimeters (0.094 in) and pertain to the thoracic region of the individual, although the exact position can no longer be assessed due to the destruction of the skeleton.[31]
In 1997, Ken Carpenter reported a damaged Tarbosaurus skull with impressions of a dewlap or throat pouch beneath the lower jaws, based on a personal communication from Konstantin Mikhailov.[32] Carpenter speculated that the pouch may have been used for display, possibly being brightly colored and inflatable like a frigatebird's.[33] In a 2019 communication to Mickey Mortimer, Mikhailov confirmed that this specimen had not been collected because it was on a heavy stone slab. He revealed that it had been discovered by Sergei Kurzanov and that it was Kurzanov himself who had originally interpreted the impressions as a throat structure.[34] This specimen may be the same as one that was purportedly destroyed by poachers in 1992.[35]
Description
Although slightly smaller than Tyrannosaurus, Tarbosaurus was one of the largest tyrannosaurines, with the type specimen PIN 551–1 measuring approximately 10 metres (33 ft) long, 3 metres (9.8 ft) tall at the hips, and weighing up to 4.5–5 metric tons (5.0–5.5 short tons).[36][37][38] The largest known Tarbosaurus skull is about 1.35 m (4.4 ft) long,[39] which is larger than that of all other tyrannosaurids, aside from Tyrannosaurus.[13]
Skull
The skull was tall, like that of Tyrannosaurus, but not as wide, especially towards the rear. The unexpanded rear of the skull meant that Tarbosaurus‘s eyes did not face directly forwards, suggesting that it lacked the
Postcranial skeleton
Tyrannosaurids varied little in overall body form and Tarbosaurus was no exception. The head was supported by an S-shaped neck, while the rest of the
Classification
Tarbosaurus is classified as a
Tarbosaurus bataar was originally described as a species of Tyrannosaurus,
The discovery of
Below is the cladogram of Tyrannosaurinae based on the
Paleobiology
Ontogeny
Most specimens of Tarbosaurus represent adult or subadult individuals, while juveniles remain very rare. Nevertheless, the 2006 discovery of a juvenile individual (MPC-D 107/7) with a complete, 290-millimeter (0.95 ft) long skull was reported and described in 2011, providing information on the life history of this dinosaur. This individual was probably 2 to 3 years old at the time of death. Compared to adult skulls, the juvenile skull was weakly constructed and the teeth were thin, indicating different food preferences in juveniles and adults that reduced competition between different age groups.[43] Examination of the sclerotic rings in this juvenile Tarbosaurus suggests they may also have been crepuscular or nocturnal hunters. Whether or not the adult Tarbosaurus were also nocturnal is currently unknown due to the lack of fossil evidence to suggest so.[44]
Senses
A Tarbosaurus skull found in 1948 by Soviet and Mongolian scientists (PIN 553–1, originally called Gorgosaurus lancinator) included the skull cavity that held the brain. Making a plaster
The endocranial structure of Tarbosaurus was similar to that of Tyrannosaurus,
The large size of the olfactory bulbs, as well as the terminal and olfactory nerves, suggest that Tarbosaurus had a highly keen sense of smell, as was also the case with Tyrannosaurus. The vomeronasal bulb is large and differentiated from the olfactory bulb, which was initially suggested as being indicative of a well-developed Jacobsen's organ, which was used to detect pheromones. This may imply that Tarbosaurus had complex mating behavior.[46] However, the identification of the vomeronasal bulb has been challenged by other researchers because they are not present in any living archosaurs.[48]
The
Skull mechanics
The skull of Tarbosaurus was completely described for the first time in 2003. Scientists noted key differences between Tarbosaurus and the North American tyrannosaurids. Many of these differences are related to the handling of stress by the skull bones during a bite. When the upper jaw bit down on an object, force was transmitted up through the maxilla, the primary tooth-bearing bone of the upper jaw, into surrounding skull bones. In North American tyrannosaurids, this force went from the maxilla into the fused nasal bones on top of the snout, which were firmly connected in the rear to the lacrimal bones by bony struts. These struts locked the two bones together, suggesting that force was then transmitted from the nasals to the lacrimals.[4]
Tarbosaurus lacked these bony struts and the connection between the nasals and lacrimals was weak. Instead, a backwards projection of the maxilla was massively developed in Tarbosaurus and fit inside a sheath formed from the lacrimal. This projection was a thin, bony plate in North American tyrannosaurids. The large backwards projection suggests that force was transmitted more directly from the maxilla to the lacrimal in Tarbosaurus. The lacrimal was also more firmly anchored to the frontal and prefrontal bones in Tarbosaurus. The well-developed connections between the maxilla, lacrimal, frontal, and prefrontal would have made its entire upper jaw much more rigid.[4]
Another major difference between Tarbosaurus and its North American relatives was its more rigid mandible. While many theropods, including North American tyrannosaurids, had some degree of flexibility between the bones in the rear of the mandible and the dentary in the front, Tarbosaurus had a locking mechanism formed from a ridge on the surface of the angular, which articulated with a square process on the rear of the dentary.[4]
Some scientists have
Bite force and feeding
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events, they are more likely to be caused by regular behavior than other types of injuries. None of the eighteen Tarbosaurus foot bones examined in the study were found to have a stress fracture, but one of the ten examined hand bones was found to have one. Stress fractures in the hands have special behavioral significance compared to those found in the feet, since stress fractures there can be obtained while running or during migration. Hand injuries, by contrast, are more likely to be obtained while in contact with struggling prey. The presence of stress fractures and tendon avulsions, in general, provide evidence for a "very active" predation-based diet instead of obligate scavenging.[54]
As for its bite force, it was revealed in 2005 that Tarbosaurus had a bite force of around 8,000 to 10,000 pounds per square inch of force, meaning that it could crush bones just like its North American relative, Tyrannosaurus.[55]
David W. E. Hone and Mahito Watabe in 2011 reported the left humerus of a nearly complete
In 2012, bite marks on two fragmentary
A 2020 study involving stable isotopes found that Tarbosaurus primarily hunted large dinosaurs in its environment, most notably titanosaurs and hadrosaurs.[58]
Paleoenvironment
The vast majority of known Tarbosaurus fossils were recovered from the
Tarbosaurus is found chiefly in the Nemegt Formation, whose sediments preserve large river channels and soil deposits that indicate a far more humid climate than those suggested by the underlying
Occasional
See also
References
- ^ a b Mortimer, M (2004). "Tyrannosauroidea". The Theropod Database. Archived from the original on September 29, 2013. Retrieved August 21, 2007.
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- ^ Doklady Akademii Nauk SSSR. 104 (4): 634–637.
- ^ a b c d e f g h i j k Hurum, Jørn H.; Sabath, Karol (2003). "Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared" (PDF). Acta Palaeontologica Polonica. 48 (2): 161–190.
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- ^ Doklady Akademii Nauk SSSR. 104 (5). translated by F. J. Alcock: 779–783.
- ^ Rozhdestvensky, Anatoly K. (1965). "Growth changes in Asian dinosaurs and some problems of their taxonomy". Paleontological Journal. 3: 95–109.
- ^ Maleev, Evgeny A. (1974). "Gigantic carnosaurs of the family Tyrannosauridae". The Joint Soviet-Mongolian Paleontological Expedition Transactions. 1: 132–191.
- ^ Barsbold, Rinchen (1983). "Carnivorous dinosaurs from the Cretaceous of Mongolia". The Joint Soviet-Mongolian Paleontological Expedition Transactions. 19: 5–119.
- ^ a b Carpenter, Ken. (1992). "Tyrannosaurids (Dinosauria) of Asia and North America". In Mateer, Niall J.; Peiji, Chen (eds.). Aspects of Nonmarine Cretaceous Geology. Beijing: China Ocean Press. pp. 250–268.
- ^ Olshevsky, George; Ford, Tracy L. (1995). "The origin and evolution of the tyrannosaurids, part 1". Dinosaur Frontline (in Japanese). 9: 92–119.
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- ^ Currie, Philip J.; Hurum, Jørn H.; Sabath, Karol (2003). "Skull structure and evolution in tyrannosaurid phylogeny"(PDF). Acta Palaeontologica Polonica. 48 (2): 227–234.
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- ^ Watabe, Masato; Suzuki, Shigeru (2000). "Cretaceous fossil localities and a list of fossils collected by the Hayashibara Museum of Natural Sciences and Mongolian Paleontological Center Joint Paleontological Expedition (JMJPE) from 1993 through 1998". Hayashibara Museum of Natural Sciences Research Bulletin. 1: 99–108.
- Currie, Philip J.(2001). "Nomadic Expeditions, Inc., report of fieldwork in Mongolia, September 2000.". Alberta Palaeontological Society, Fifth Annual Symposium, Abstract Volume. Calgary: Mount Royal College. pp. 12–16.
- Currie, Philip J.(2002). "Report on fieldwork in Mongolia, September 2001.". Alberta Palaeontological Society, Sixth Annual Symposium, 'Fossils 2002,' Abstract Volume. Calgary: Mount Royal College. pp. 8–12.
- ^ Switek, Brian (May 19, 2012). "Stop the Tarbosaurus Auction!". Wired.
- ^ Black, Riley (January 9, 2013). "The Million Dollar Dinosaur Scandal". Slate. Retrieved June 6, 2021.
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- ^ Williams, Paige (January 28, 2013). "Bones of Contention". The New Yorker. Retrieved September 9, 2017.
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- ^ Brusatte, Hone and Xu, 2013. Phylogenetic revision of Chingkankousaurus fragilis, a forgotten tyrannosauroid from the Late Cretaceous of China. in Parrish, Molnar, Currie and Koppelhus (eds.). Tyrannosaurid Paleobiology. Indiana University Press. 1–13.
- ^ Kurzanov, Sergei M. (1976). "A new Late Cretaceous carnosaur from Nogon−Tsav, Mongolia". The Joint Soviet-Mongolian Paleontological Expedition Transactions (in Russian). 3: 93–104.
- ^ Currie, Philip J. (2003). "Cranial anatomy of tyrannosaurids from the Late Cretaceous of Alberta" (PDF). Acta Palaeontologica Polonica. 48 (2): 191–226. Archived from the original(PDF) on June 21, 2007.
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- ^ Mortimer, M. (2019). "Tarbosaurus bataar – Skin impressions". The Theropod Database. Retrieved November 21, 2020.
- ^ Watabe, M.; Suzuki, S. (2000). "Report on the Japan-Mongolia Joint Paleontological Expedition to the Gobi desert, 1993". Hayashibara Museum of Natural Sciences Research Bulletin. 1: 19–29.
- ^ Holtz, Thomas R. Jr. (2012). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages (PDF). Archived (PDF) from the original on October 2, 2022.
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- ^ Maleev, Evgeny A. (1965). "On the brain of carnivorous dinosaurs". Paleontological Journal (in Russian). 2: 141–143.
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- ^ Gallagher W.B., Tumanova T.A., Dodson P., Axel L., 1998, "CT scanning Asian ankylosaurs: paleopathology in a Tarchia skull", Journal of Vertebrate Paleontology 18: 44A-45A
- ^ Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.
- ^ Therrien, Francois; Henderson, Donald M.; Ruff, Christopher B. (January 2005). "Bite me: Biomechanical models of theropod mandibles and implications for feeding behavior". In Kenneth Carpenter (ed.). The Carnivorous Dinosaurs. Indiana University Press. pp. 179–237. Retrieved November 11, 2018.
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External links
Images and photos
- Skeletal image of Shanshanosaurus at The Grave Yard.
- Comparison between Tarbosaurus skulls from specimens of different age group and size.
Readable material
- Discussion and specimen list at The Theropod Database.
- Review of the Tyrannosauridae by George Olshevsky (1995).
- Scienceblogs: Juvenile, 5 years old Tarbosaurus specimen found in Mongolia 2006.